high frequency intermittent noise

I did lots of research into balanced power a while back and although I went with a different unit for monetary reasons this is the unit I would have purchased. Yes, it's professional grade but so what? If it takes care of your problem then it’s worth it.

http://www.furmanpower.com/product/20a-prestige-symmetrically-balanced-power-conditioner-P-2400%20IT

@almarg I checked 540kHz and for a moment, I thought I was in that movie Contact, I did not hear the noise.  Just static.  Great idea.

@falconquest Thank you for the pointer, I will check that out.

Make sure you look at a Furman with LiFT and SMP.

The SMP surge protection is, by design, a low pass filter. Unlike most other AC filters it works in the audible band, but not sure how low.

LiFT is active filtration. The one thing about Furman, they seem to have 100 different models, so be careful that the exact model you look at or test includes both.

Not sure about common mode noise, but most linear power transformers filter that out anyway.

James, one other thing to try, use an extension cord if you must, but maybe you have other AC lines which are less noisy, or perhaps a place in your apartment where the noise pickup is less?

Just throwing out ideas that are cheap. :)

But yeah, I like Furman for noise and value (especially if you can find them on sale!)

@erik_squires The Furman looks promising.  The P 2400 IT looks like the way to go.